The present invention relates generally to hardcopy devices, particularly but not exclusively to inkjet printers and to a method of servicing such devices.
As is well known in the art, conventional inkjet printers generally employ one or more inkjet cartridges, often called xe2x80x9cpensxe2x80x9d, which eject drops of ink onto a page or sheet of print media. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to Hewlett-Packard Company. The pens are usually mounted on a carriage, which is arranged to scan across a scan axis relative to a sheet of print media as the pens print a series of individual drops of ink on the print media. The series of drops collectively form a band or xe2x80x9cswathxe2x80x9d of an image, such as a picture, chart or text. Between scans, the print medium is advanced relative to the scan axis. In this manner, an image may be incrementally printed.
In order to ensure satisfactory print quality, a xe2x80x9cservice stationxe2x80x9d apparatus is typically located within the printer chassis, laterally offset to one side of the printzone, so that the printheads can be periodically moved to a servicing position and serviced. Such service stations usually include a number of elastomeric wipers, used to wipe the printhead surface with an ink solvent, such as a polyethylene glycol (xe2x80x9cPEGxe2x80x9d) compound, to remove any ink residue, paper dust, or other matter that has collected on the face of the printhead. Additionally, service stations usually include one or more reservoirs, termed xe2x80x9cspittoonsxe2x80x9d which are designed to receive and store drops of ink ejected during xe2x80x9cspittingxe2x80x9d operations. xe2x80x9cSpittingxe2x80x9d is the term given to the process by which a number of ink drops are fired through one or more nozzles of a printhead in order to remove a blockage in the nozzle caused by dried ink or other matter. Service stations may also include a capping system that seals and protects the printhead nozzles from contaminants and drying out during non-printing periods. One example of a servicing station for an inkjet device is disclosed in U.S. Pat. No. 6,203,135 entitled xe2x80x9cIndependent Servicing Of Multiple Inkjet Printheadsxe2x80x9d, in the name of Hewlett-Packard Co.
Between printing consecutive passes over the print zone, the carriage must reverse direction. This entails decelerating from the printing speed of the printer to zero and reaccelerating back to the printing speed in the reverse direction. This process is generally carried out outside the print zone in order to allow the printing process to be carried out at a constant printing speed. Consequentially, the scan axis must extend on either side of the print zone by a distance that is at least equal to this xe2x80x9cturn aroundxe2x80x9d distance. In practice, the size of inkjet service stations means that they generally extend from the edge of the print zone by a distance that is even greater than the xe2x80x9cturn aroundxe2x80x9d distance. Consequently, the size of service stations often contributes directly to the footprint of the printer.
Printers with xe2x80x9csplitxe2x80x9d service stations address this problem by locating a reduced width service station within the xe2x80x9cturn aroundxe2x80x9d distance at either side of the print zone. Different pens are then serviced at different sides of the print zone. By using this service station configuration, the degree to which the size of service station contributes to the footprint of the printer may be significantly reduced, or eliminated. Thus, the footprint of the printer may be correspondingly reduced. One example of an inkjet printer device with a reduced footprint is disclosed in U.S. Pat. No. 6,270,183, assigned to Hewlett-Packard Company.
Over recent years the importance placed on the throughput of inkjet printers has risen dramatically. Throughput is generally measured as the number of pages of a given size, or the area of print media that a printer may ink in a given time. One factor that has a negative impact on the throughput of an inkjet printer is the time required to service the printheads.
It would therefore be desirable to provide an inkjet apparatus and method for servicing such devices, which addresses this issue.
According to one aspect of the present invention there is provided an inkjet printing device comprising a print zone and first and second printheads mounted to a carriage arranged to traverse said print zone, said device further comprising first and second service stations arranged to service said first and second printheads respectively, said service stations being located such that said carriage has first and second servicing positions to allow the servicing of said first and second pens respectively, said device being arranged to print in a first print mode in which said first printhead is not used and being further arranged not to service said first printhead whilst printing in said first print mode.
In a printer device that has split service stations and is adapted to print in a reserve mode when a pen fails, a significant amount of time may be saved in servicing routines by deselecting the failed pen from servicing. This is because split servicing is, generally speaking, a series process. This means that one pen, which is serviced at a first side of the printzone, is serviced first and subsequently another pen is serviced at a second side of the print zone. This is in contrast to conventional, non-split servicing printers, where all pens may be simultaneously serviced. Thus, whereas there is no extra time overhead associated with servicing a failed pen in convention, non-split servicing printers, this is not the case in split serviced printers.
Thus, by avoiding servicing a failed pen in a split service printer, time savings come from two main sources: firstly, from the time that is saved by not having to move the failed pen across the print zone to its service station; and, secondly, from the time that is saved by not implementing the actual servicing routine with regard to the failed pen, for example a splitting routine. Advantageously, the time saved in such servicing routines may result in a direct increase in the throughput of the printer.
A further advantage of the present invention is that it may reduce the amount of airborne ink droplets, termed aerosol, which are generated by spitting operations. Even though a pen, printer cartridge or printhead may be deemed to have failed, and thus not be used for printing, it may still be able to spit ink from some nozzles during spitting routines. Such aerosol droplets can cause many problems in printers. For example, airborne droplets may stain any areas with which they come into contact. Thus, the may reduce the effectiveness of optical devices and sensors used in the printer. Additionally, however, aerosol ink of one colour may contaminate the ink supply or servicing modules of another ink colour. This may lead to a visible deterioration in the quality of the printed output of the printer.
The present invention also extends to the corresponding method. Furthermore, the present invention also extends to a computer program, arranged to implement the method of the present invention.